Definition of a Computer (was: Totally OT, but frustrated.....

[Tony Duell]

> 
> Rumor has it that Tony Duell may have mentioned these words:
> 
> >OK (and this came up in some private e-mail when discussing the major
> >off-topic threads here). What is a computer? Becasue I certainly don't 
> >have an exact definition.
> 
> I always heard it defined (and seemed the most logical/sensible to me) as:
> 
> "A computer is a device which can perform arithmetic _and_ logical 
> functions without the aid of a human."

Ah, but analogue computers don't perform logical functions....

And how much 'aid' does ther human have to provide? Most machines need to 
be turned on ;-). Often a human selects what program to run and what 
inputs to give it.

> 
> Several of my earlier computing textbooks put it in this manner, explained 
> why it was so (see below) and it's always worked for me.
> 
> That said, a 4-function calculator was not a computer (if that's all the 
> underlying hardware could handle[1]), but just about any programmable 

Yes, but to divide two floating-point numbers requires quite a sequence 
of operations (you try working out how to do it on a machine without even 
a full adder... [2]). Does that count as 'performing arithmetic and 
logical functions without the aid of a human'? 

[2] OK, not a 4-function machine, but this does describe the HP9100.

> calculator was, if it had any type of control looping abilities, as that's 
> the "logical function" aspect of the definition.

I think this illustrates my point. It's easy to find things that are 
definitely computers (the PDP11 in the next room, for example, the PC I 
am typing this on), and things that are certainly not computers (the 
camera sitting on top of said PC). THe problem comes with the boarderline 
cases -- like the programmable calculator with no looping constructs 
other than an automatic return-to-start at the end of the program.

-tony